This invention is directed to improvements in gun muzzle deflection detector means of the general type shown in U.S. Pat. No. 3,684,383 to Johansson and U.S. Pat. No. 4,142,799 to Barton. Each of these patents discloses an optical system wherein a light beam is directed forwardly along the barrel of a main gun on a military vehicle to impinge on a mirror located on the muzzle end of the gun. The light beam is reflected rearwardly to an optical sensor located at or near the breech end of the gun; in the case of a trunion-mounted gun the sensor is located as close as possible to the trunion axis to maintain an invariant optical system as the gun elevational angle changes during firing operations. The optical system detects deflection of the gun muzzle in the elevation and/or azimuth directions due to such factors as gravity, thermal bending caused by sun striking the barrel upper surface, uneven barrel cooling due to rain or wind, uneven heating due to firing, cross winds, etc.
The present invention contributes to this general system an optical detector comprised of a depletion mode linear photodiode sensor having four output terminals oriented, respectively directly above, directly below, directly to the right, and directly to the left of the detector optical axis representing zero gun muzzle deflection. The four outputs are combined and amplified to provide input corrective signals to a main gun ballistic computer.